Expression and characterization of two STAT isoforms from Sf9 cells.

In invertebrates, the JAK-STAT signaling pathway is involved in the anti-bacterial response and is part of an anti-viral response in Drosophila. In this study, we show that two STAT transcripts are generated by alternative splicing and encode two isoforms of Sf-STAT with different C-terminal ends. These two isoforms were produced and purified using the recombinant baculovirus technology. Both purified isoforms showed similar DNA-binding activity and displayed weak but significant transactivation potential toward a Drosophila promoter that contained a STAT-binding motif. No significant activation of the Sf-STAT protein in Sf9 cells was found by infection with baculovirus AcMNPV.